Crude oils and middle distillates obtained by distillation of crude oils such as gas oil, diesel oil or heating oil contain varying amounts of paraffin, which can form precipitates. In the case of crude oil, the paraffin in usually liquefied and stabilized in the crude oil under high temperatures encountered at the downhole. However, as the oil is brought to the surface its temperature is reduced. As a result, the paraffin may begin to precipitate out and may form deposits on any cooler surface with which they come into contact. These wax deposits can cause problems, such as blockage of pipelines, valves and other process equipment. The wax may also deposit in pipelines subsequently used to transport crude oil or fractions thereof including hydrocarbon lines or multiphase transportation lines with oil, gas and/or water.
The contents of the transport pipelines are often cooler than the contents of lines on oil platforms or in refineries. This cooling is especially critical in respect of lines from offshore oil fields to the land and landlines in winter or in cold territories.
With respect to crude oil distillates such as diesel fuel or heating oil, precipitation of paraffin results in the impairment of the flow properties of the fuel, which can result in problems during their recovery, transport, storage and/or use. In winter, for example, it may in certain instances be necessary to store the fuels in heated tanks. Precipitation of paraffin can also result in blockage of the filters in diesel engines and furnaces, preventing reliable metering of the fuels and in some cases causing complete interruption of the supply of fuel.
Wax deposition may be reduced in a number of ways, including keeping the lines hot, diluting the oil with solvent, or using additives, which interfere with wax crystal growth.
Typical additives include wax crystal modifiers, pour point dispersants, paraffin deposition inhibitors, and the like. Most additives are polymeric in nature. However, due to the polymeric nature and associated molecular weights, these typically have problems with handling, especially in low temperature applications. Therefore, the additives are generally diluted to about 5% active concentration or below for capillary or umbilical (deep water) delivery of chemicals. Yet, this results in the use of tremendous volume of products, especially solvents, resulting in increased costs for shipping, storage, and ultimately production of the oil. Also, the excessive amount of organic solvents, predominantly aromatics, can cause significant environmental problems.